We will use the Sandison-Clark rabbit ear chamber vascular model in the New Zealand white male rabbit to evaluate the effects of graded single X-ray doses, fractionated X-ray exposures, graded doses of chemotherapeutic agents and the interaction of these agents. Early and late vascular changes will be scored and correlated singly or in combination. The following parameters will be measured in vivo: 1. Microvascular length (less than or equal to 10 microns diameter, greater than 10 microns diameter); 2. Vascular surface area (less than or equal to 10 microns diameter, greater than 10 microns diameter); 3. Vascular density/mm squared for: a. capillaries less than or equal to 10 microns diameter, b. larger vessels greater than 10 microns diameter, and c. total microvasculature; 4. Vascular supportive tissue surface area. In vitro studies, using comparable primary cultures of vascular endothelial and smooth muscle cells, will be carried out in parallel to elucidate further the role of the two most reactive vascular cell populations in early and late radiation effects, as well as possible potentiation by combination with chemotherapy. This approach will provide quantitative data and new insight into the interaction of these two agents widely used in tumor therapy.